×

Warning message

  • Cisco Support Forums is in Read Only mode while the site is being migrated.
  • Cisco Support Forums is in Read Only mode while the site is being migrated.
Jon Marshall Mon, 11/25/2013 - 02:48
User Badges:
  • Super Blue, 32500 points or more
  • Hall of Fame,

    Founding Member

  • Cisco Designated VIP,

    2017 LAN, WAN

Chandu


A vlan is a broadast domain as you say but it is not necessarily reduced because it depends on how many devices you have in that vlan. But is it is virtual in the sense that a vlan can span multiple switches or even sites whereas before vlans devices were constrained to the same physical location if they were on the same subnet.


Jon

Joseph W. Doherty Mon, 11/25/2013 - 03:25
User Badges:
  • Super Bronze, 10000 points or more

Disclaimer


The  Author of this posting offers the information contained within this  posting without consideration and with the reader's understanding that  there's no implied or expressed suitability or fitness for any purpose.  Information provided is for informational purposes only and should not  be construed as rendering professional advice of any kind. Usage of this  posting's information is solely at reader's own risk.


Liability Disclaimer


In  no event shall Author be liable for any damages whatsoever (including,  without limitation, damages for loss of use, data or profit) arising out  of the use or inability to use the posting's information even if Author  has been advised of the possibility of such damage.


Posting


A VLAN is what it's named, a Virtual LAN.  Basically, it allows multiple logical LAN (separate L2 network segments - i.e. your broadcast domain) to run side-by-side on the same physical switch (rather than separate physical LAN segments on different physical switches).  As Jon noted, per se, it doesn't mean such must be smaller, but as it can be done logically, often implementations are "smaller" because we don't need to find and connect multiple physical switches.  For example, one VLAN capable 48 port switch might support 24 VLANs each containing just 2 ports, avoiding the need of using 24 physical switches for the same L2 isolation.


PS:

BTW, some newer switches have special VLAN capabilities, such a PVLANs (private VLANS) that wouldn't be easy to define with physical switches.

chandra_rc16 Mon, 11/25/2013 - 03:47
User Badges:

Actually, i'm trying to define. VLAN in a single line. Because i'm preparing a presentation cum documentation.

Can i say like this:


A VLAN is nothing but a logical switch on a physical switch.


Regards,

Chandu

Jon Marshall Mon, 11/25/2013 - 04:01
User Badges:
  • Super Blue, 32500 points or more
  • Hall of Fame,

    Founding Member

  • Cisco Designated VIP,

    2017 LAN, WAN

No you can't really because a vlan can exist across multiple switches.


This would be my definition but others may  have better ones -


A vlan is a logical grouping of end devices into the same L2 broadcast domain (LAN) even though those devices may be located on multiple different switches which may or may not be in the same physical location.


Jon

chandra_rc16 Mon, 11/25/2013 - 04:30
User Badges:

-------

No you can't really because a vlan can exist across multiple switches.

-------


Yes it exits on multiple physical switches but VLAN is a logical switch on all those multiple physical switches. So i think i can like that..


But still need the feedback on this. Because it is very important for me.


Regards,

Chandu

Jon Marshall Mon, 11/25/2013 - 04:39
User Badges:
  • Super Blue, 32500 points or more
  • Hall of Fame,

    Founding Member

  • Cisco Designated VIP,

    2017 LAN, WAN

I see what you mean now. I thought you were talking about a single physical switch.


But in my opinion referring to a vlan as switch is missing the point. A vlan is primarily a L2 broadcast domain that is simply logical in terms of where the end devices are connected rather than physical. This says nothing about how may vlans you have per switch. 

Jon

chandra_rc16 Tue, 11/26/2013 - 02:39
User Badges:

I think this is more appropriate.


VLAN is used to logically group devices and to isolate different types of traffic


Regards,

Chandu

Actions

This Discussion